The present invention relates generally to microsurgical instruments and more specifically, but not by way of limitation, to microsurgical instruments suitable for creating a corneal pocket incision for the implantation of intracorneal optical lenses (ICOLs).
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens.
The optical power of the eye is determined by the optical power of the cornea and the crystalline lens. In the normal, healthy eye, sharp images are formed on the retina (emmetropia). In many eyes, images are either formed in front of the retina because the eye is abnormally long (axial myopia), or formed in back of the retina because the eye is abnormally short (axial hyperopia). The cornea also may be asymmetric or toric, resulting in an uncompensated cylindrical refractive error referred to as corneal astigmatism. In addition, due to age-related reduction in lens accommodation, the eye may become presbyopic resulting in the need for a bifocal or multifocal correction device.
In the past, axial myopia, axial hyperopia and corneal astigmatism generally have been corrected by spectacles or contact lenses, but there are several refractive surgical procedures that have been investigated and used since 1949. Barraquer investigated a procedure called keratomileusis that reshaped the cornea using a microkeratome and a cryolathe. This procedure was never widely accepted by surgeons. Another procedure that has been used is radial and/or transverse incisional keratotomy (RK or AK, respectively). Photoablative lasers have also been used to reshape the surface of the cornea (photorefractive keratectomy or PRK) or for mid-stromal photoablation (Laser-Assisted In Situ Keratomileusis or LASIK). All of these refractive surgical procedures cause an irreversible modification to the shape of the cornea in order to effect refractive changes, and if the correct refraction is not achieved by the first procedure, a second procedure or enhancement must be performed. Additionally, the long-term stability of the correction is variable because of the variability of the biological wound healing response between patients.
Permanent intracorneal implants made from synthetic materials are also known for the correction of corneal refractive errors. Such implants may be generally classified into two categories.
One category is intracorneal implants that have little or no refractive power themselves, but change the refractive power of the cornea by modifying the shape of the anterior surface of the cornea. U.S. Pat. No. 5,123,921 (Werblin, et al.); U.S. Pat. Nos. 5,505,722, 5,466,260, 5,405,384, 5,323,788, 5,318,047, 5,312,424, 5,300,118, 5,188,125, 4,766,895, 4,671,276 and 4,452,235 owned by Keravision and directed to intrastromal ring devices; and U.S. Pat. No. 5,090,955 (Simon), U.S. Pat. No. 5,372,580 (Simon, et al.), and WIPO Publication No. WO 96/06584 directed to Gel Injection Adjustable Keratoplasty (GIAK) all disclose examples of this category of implant.
A second category is intracorneal implants having their own refractive power. U.S. Pat. No. 4,607,617 (Choyce); U.S. Pat. No. 4,624,669 (Grendahl); U.S. Pat. No. 5,628,794 (Lindstrom); and U.S. Pat. Nos. 5,196,026 and 5,336,261 (Barrett, et al.) provide several examples of this category. In addition, U.S. patent application Ser. No. 08/908,230 filed Aug. 7, 1997 entitled xe2x80x9cIntracorneal Diffractive Lensxe2x80x9d, which is incorporated herein in its entirety by reference, discloses an example of an ICOL that has both refractive and diffractive powers.
Microsurgical instruments used for the implantation of such intracorneal implants have also been developed. For example, WIPO Publication No. WO 99/30645 owned by Keravision discloses a variety of instruments for surgically implanting ring-shaped intracorneal implants and ICOLs. These tools may be used manually, but are preferably used in cooperation with a vacuum centering device. The surgical procedures described in this publication require multiple instruments to form an intracorneal ring-shaped channel or an intracorneal pocket. In addition, the use of a vacuum centering device increases the expense of the surgical procedure.
Accordingly, a need exists for a microsurgical instrument that more effectively creates an intracorneal pocket for the implantation of an ICOL. The instrument should be easy for the surgeon to use, should maximize patient safety, and should be economically feasible. The instrument should eliminate the need for multiple tools for forming the intracorneal pocket.
One aspect of the present invention is a microsurgical instrument having a handle and a dissecting tip coupled to the handle. The handle includes a cannula for transporting surgical fluid. The dissecting tip includes a blade for dissecting tissue and an aperture for delivering the fluid.
Another aspect of the present invention is a method of creating an intracorneal pocket for the implantation of an intracorneal optical lens. A microsurgical instrument is provided. The instrument has a handle and a dissecting tip coupled to the handle. The handle includes a cannula for fluidly coupling to a reservoir of surgical fluid. The dissecting tip includes a blade for dissecting tissue and an aperture for delivering the fluid. The dissecting tip is inserted into an incision into a cornea. The reservoir is activated to eject the surgical fluid from the aperture. The intracorneal pocket is created by moving the tip in an arcuate, planar manner. The surgical fluid facilitates the dissection of stromal tissue. The surgical fluid also lubricates the dissecting tip so as to minimize irritation of stromal tissue.